bug#14582: 24.3.50.1; Strange overlay behavior, when window-start is inside an overlay.

[Eli Zaretskii]

> From: Michael Heerdegen <michael_heerdegen@web.de>
> Cc: larsi@gnus.org,  esabof@gmail.com,  14582@debbugs.gnu.org
> Date: Thu, 10 Feb 2022 02:07:19 +0100
> 
> Eli Zaretskii <eliz@gnu.org> writes:
> 
> > Info buffers have a 'display' property whose value is a string at the
> > beginning of each node, and that 'display' property makes the window's
> > start point invisible.  So whenever Emacs can make the window-start
> > visible, it does.
> 
> But Emacs scrolls the first lines out of view: at the upper edge, less
> text is visible after the adjustment.  How does this make anything
> visible that had not been visible before?

That's not what make-window-start-visible means.  It means "if the
current window-start is invisible, try to find an alternative
window-start that would be visible, while still showing point".

Your interpretation of the setting is simply impossible to implement:
the display engine cannot possibly do anything to uncover the hidden
window-start point without scrolling the window in some way.  So
_something_ that was visible before must become invisible after,
because we scroll the window.